From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from butterbrot.org ([176.9.106.16]:35268 "EHLO butterbrot.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097AbbCWL5k (ORCPT ); Mon, 23 Mar 2015 07:57:40 -0400 Message-ID: <550FFFB2.9020400@butterbrot.org> Date: Mon, 23 Mar 2015 12:57:38 +0100 From: Florian Echtler MIME-Version: 1.0 To: linux-input , LMML , Hans Verkuil , Benjamin Tissoires , Dmitry Torokhov Subject: [sur40] Debugging a race condition? Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="oPPxg8R8TTkaQLuKXcSWcgG4WgxwvBOPi" Sender: linux-media-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --oPPxg8R8TTkaQLuKXcSWcgG4WgxwvBOPi Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hello everyone, now that I'm using the newly merged sur40 video driver in a development environment, I've noticed that a custom V4L2 application we've been using in our lab will sometimes trigger a hard lockup of the machine (_nothing_ works anymore, no VT switching, no network, not even Magic SysRq). This doesn't happen with plain old cheese or v4l2-compliance, only with our custom application and only under X11, i.e. as far as I can tell, when the input device is being polled at the same time. However, I have a really hard time tracking this down, as even SysRq doesn't work anymore. A console continuously dumping dmesg or strace of our tool didn't really help, either. I assume that somehow the input_polldev thread is put to sleep/waiting for a lock due to the video functions and that causes the lockup, but I can't really tell where that might happen. Can somebody with better knowledge of the internals give some suggestions? Thanks & best regards, Florian --=20 SENT FROM MY DEC VT50 TERMINAL --oPPxg8R8TTkaQLuKXcSWcgG4WgxwvBOPi Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlUP/7IACgkQ7CzyshGvatjtBwCfXCjOWidGRK09OBHZI4LoxamV kKYAoJtLqrrBJpJJmdUXlZrlfwD23Drn =fDSX -----END PGP SIGNATURE----- --oPPxg8R8TTkaQLuKXcSWcgG4WgxwvBOPi--